Strains of dengue virus will be transmitted in the laboratory using Aedes aegypti mosquitoes from several geographic areas to assess their relative vector competence. Fluorescent antibody will be used to assay for antigen in mosquitoes and hanging drop feeding techniques to effect transmission. The CER cell will be used with a wide variety of rhabdoviruses, some of them newly recognized, to develop assays for serological and biochemical studies. HI comparison of VSV and rabies serogroup viruses to establish the taxonomic position of these viruses is planned. Neutralization tests in mice with 5 geographic strains of Crimean hemorrhagic fever-Congo virus will be carried out and the already initiated fluorescent focus inhibition study will be completed. These tests will establish whether geographic variants exist.